A revised model of the hydraulic fracture (HF)
formulation [1] that accounts for the hydraulically induced shear stress at the
crack faces is discussed. It is shown that, due to the order of the tip
singularity of the hydraulic shear stress, this component of the load cannot be
omitted in the analysis. The amended crack propagation criterion based on the
critical value of the energy release rate is derived. A new parameter, the
fluid shear stress intensity factor, is introduced and has proved to play an
important role in the HF process. It is also shown that the shear stress
induced by viscous fluid at the crack faces influences the crack propagation
direction in the mixed mode fracture [2].
Numerical simulations have highlighted advantages of the
revised HF model. In particular, the small toughness regime is no longer
presents a significant computational challenge. The modified formulation opens
new ways not only to analyse the physical phenomenon of HF, but for improving
the reliability and efficiency of its numerical simulation as well.
[1] Wrobel, M., Mishuris, G., Piccolroaz, A. 2017. Energy
release rate in hydraulic fracture: Can we neglect an impact of the
hydraulically induced shear stress? International Journal of Engineering
Science. 111 pp. 28-51.[2] Perkowska, M., Piccolroaz, A., Wrobel, M., Mishuris, G.
2017. Redirection of a crack driven by viscous fluid. International Journal
of Engineering Science 121 pp. 182-193.